Priority Populations
The “anurans” species group consists of seven frog and one toad species: American toad (Bufo americanus), American bullfrog (Lithobates catesbeianus), green frog (Lithobates clamitans), Cope’s gray treefrog (Hyla chrysoscelis), eastern gray treefrog (Hyla versicolor), northern leopard frog (Lithobates pipiens), spring peeper (Pseudacris crucifer), and wood frog (Lithobates sylvaticus). All 8 species have been documented recently in the LGBFR AOC by the Great Lakes Coastal Wetland Monitoring Program (CWMP, 2011-2017; Uzarski et al. 2017) and additional field surveys conducted for this project in 2015. These records include audio recordings archived at the UW-Green Bay’s Cofrin Center for Biodiversity. According to 1981-1995 data collected for the Wisconsin Frog and Toad Survey, pickerel frog (Lithobates palustris) and boreal/western chorus frog (Pseudacris maculate/triseriata) both were reported at two locations in Brown County, Wisconsin (Mossman et al. 1998). Other Great Lakes anuran species not present in the LGBFR AOC include Fowler’s toad (Anaxyrus fowleri), which occurs in southern/eastern Great Lakes states, Blanchard’s cricket frog (Acris crepitans), found primarily in southern Wisconsin, and mink frog (Lithobates septentrionalis), which mostly occurs in northern Wisconsin (Wisconsin Herp Atlas Project 2007). To our knowledge, none of these three species have ever been detected in the LGBFR AOC.
Within the LGBFR AOC, anurans use a variety of habitats during the breeding and post-breeding seasons. We formally summarized CWMP and LGBFR AOC anuran survey data from 2011 to 2015 in Great Lakes coastal wetlands and inland marshes and investigated anuran habitat use and occurrences in the LGBFR AOC (Otto et al. 2017). During the breeding season, not surprisingly, most anurans tended to occur near emergent marshes, open water, and wet forests. Anuran species diversity was the highest along the lower bay’s west shore with few to no anurans found along the heavily developed Fox River. Green frogs tended to occur most commonly along the east shore, while American toads were more common along the west shore. A comprehensive analysis of anuran communities in the bay of Green Bay’s Great Lakes coastal wetlands and the response of these communities to changing water levels can be found in Gnass Giese et al. (2018) using CWMP 2011-2017 data. We found that green frogs tended to occur along the eastern shore in the middle and upper regions of the bay, while northern leopard frogs and spring peepers were more frequently detected along the west shore (Gnass Giese et al. 2018). However, the LGBFR AOC supported fewer anurans compared to wetlands of the middle and upper bay (Gnass Giese et al. 2018), likely because habitats in the more urbanized lower bay are degraded by invasive species, shoreline degradation, and water pollution. Gray treefrog (eastern and Cope’s combined) and American toad were the most frequently detected anuran species in the LGBFR AOC based on 2011-2017 CWMP field data.
Like many plants and animals, anurans are affected by both short-term (daily seiches) and long-term changes in water levels, at least in coastal emergent marshes (Gnass Giese et al. 2018). Generally, more anuran species and individuals are present during periods of higher lake levels; American bullfrog, green frog, northern leopard frog, and wood frog are positively associated with higher waters, while American toad is the only local species that is negatively associated with water levels (Gnass Giese et al. 2018). American bullfrogs are more abundant in LGBFR AOC coastal wetlands than in wetlands farther north in Green Bay, unlike the other anurans that are more abundant in the middle and upper bay wetlands (2011-2017 data).
Little historical information about anurans in the LGBFR AOC has been formally summarized; however, because emergent marshes and other coastal habitats historically were much more widespread in lower Green Bay (Bosley 1978), overall abundance and diversity of anurans almost certainly have decreased significantly during the last century. Historical Brown County air photos (e.g., 1938 and 1960, Brown County Planning and Land Services, Official GIS Map of Brown County, WI) show extensive emergent/submergent marshes in the Duck Creek Delta, Dead Horse Bay/Longtail Point, Peters Marsh, and along the western side of the Fox River by the De Pere Dam. The destruction and fragmentation of the coastal zone of lower Green Bay is already visible in the 1938, and wetland destruction continued through 1960 and later air photos. The long-term Wisconsin Frog and Toad Survey began in 1981 in response to noticeable declines of species such as northern leopard frog and American bullfrog (Mossman et al. 1998). Between 1981 and 1995, pickerel frog and chorus frog were both reported in two locations in Brown County, Wisconsin (Mossman et al. 1998), but neither species has been reported recently despite multiple survey efforts in the LGBFR AOC (e.g., CWMP; Uzarski et al. 2017). Statewide since the 1980s, northern leopard frog and American toad populations have been declining (Kitchell et al. 2016). Other than results from the Wisconsin Frog and Toad Survey and the Wisconsin Herpetological Atlas, the most significant historical account of anurans in Green Bay described an outbreak of at least 175 million northern leopard frogs over just two days in local marshes of Oconto during the summer of 1952 (Waldron 1953). The lower bay was almost certainly very productive as well during this time.
Anurans are important because they prey on aquatic species, including insects and other invertebrates that depend on the coastal or nearshore environment. These critical coastal areas in lower Green Bay are vulnerable to environmental contaminants such as pesticides, heavy metals, and polychlorinated biphenyls (PCBs; Qualls et al. 2013). It is well documented that anurans are highly sensitive to toxins and, if exposed in large amounts, can result in deformities and reproductive issues (Kersten 1997, Rosenshield et al. 1999, Qualls et al. 2013). Out of the eight anurans reported in the LGBFR AOC, American bullfrog and northern leopard frog are listed as state special concern species, though American bullfrog is also state ranked as “vulnerable” (S3). The original RAP stated that the LGBFR AOC needs to contain “healthy, self-sustaining, naturally reproducing, and diverse populations of…amphibians (including spring peepers, leopard frogs, American toads, eastern gray tree frogs, green frogs, bullfrogs, and salamanders)” (Wisconsin Department of Natural Resources 2016a), which was clearly necessary due to the significant loss of marshes for this group to breed.
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Wisconsin is home to eight species of bats, excluding the Indiana bat (Myotis sodalis), which was recorded only once in 1954, but including the evening bat (Nycticeius humeralis), newly documented in 2016. Four of Wisconsin’s cave-roosting bats (big brown bat, Eptesicus fuscus; little brown bat, Myotis lucifugus; northern long-eared bat, Myotis septentrionalis; and tri-colored bat [eastern pipistrelle], Perimyotis subflavus) are listed as threatened in the state. All four of these have been recorded in the LGBFR AOC study area, as have three of the other Wisconsin bats (silver-haired bat, Lasionycteris noctivagans; eastern red bat, Lasiurus borealis; and hoary bat, Lasiurus cinereus), known as “tree bats” because of their use of trees for roosting. In 2015 the northern-long-eared bat was listed as a federally threatened species under the U.S. Endangered Species Act. Silver-haired bat, while not endangered or threatened, is listed as “special concern” in Wisconsin and has a global rank of G3G4 (G3 = vulnerable, G4 = apparently secure) by NatureServe.
Populations of bats in Wisconsin and elsewhere in eastern North America are declining rapidly, partly due to a devastating disease (white-nose syndrome, WNS) caused by the fungus Psuedogymnoascus destructans. Between 2006 and 2008, cave bat declines exceeded 75% at surveyed hibernacula in eastern states (Blehert et al. 2009). WNS was first recorded in Wisconsin bats in 2016, and the threat of this epidemic (Langwig et al. 2015) has been the primary motivation for endangered/threatened listings of Wisconsin bat species that were, until recently, common and widespread in the state and throughout the Midwest. Other factors that have affected declines in tree-dwelling bats include mortality at wind turbines (Cryan and Barclay 2009) and habitat loss or degradation (Campbell et al. 1996, Crampton et al. 1998), and all bats may be vulnerable to the physiological effects of organic contaminants (Bayat et al. 2014).
Continued declines in Wisconsin bats may have severe ecological and perhaps even economic consequences. Boyles et al. (2011) estimated that insect predation by bats saves the U.S. agricultural industry $22.9 billion/year by preventing crop losses and reducing pest control expenses. The value of pest control by bats in managed forests has not been estimated, but it, too, must be worth billions of dollars annually. A single colony of 150 big brown bats consumes approximately 1.3 million insect pests each year, disrupting the population dynamics of species that otherwise would require expensive and often environmentally harmful control measures.
UW-Green Bay students Jeremiah Shrovnal and Jessica Kempke conducted acoustic bat surveys in the coastal zone of Green Bay during 2013 and 2016. Their results help set the stage for our assessment and recommendations for bat conservation in the LGBFR AOC. Kempke’s study using stationary bat detectors showed that two LGBFR AOC sites, Barkhausen Waterfowl Preserve and Point au Sable, had frequent bat activity during both migration periods (spring and fall) and during summer. Stations located near the shoreline yielded consistently higher numbers of bats than stations located farther inland at Point au Sable and other localities outside the LGBFR AOC, but not at Barkhausen. All seven of northeastern Wisconsin’s native bats were recorded at Kempke’s stations. Shrovnal sampled bats at standardized walking transects during June-September 2016. Again, transects near the shoreline yielded more bat detections than transects located farther inland. West shore transects yielded higher bat numbers than transects from the east shore, but transects along either shoreline were more productive than transects along the Fox River portion of the LGBFR AOC. Big brown bat was by far the most frequently recorded species. Little brown bat, northern long-eared bat, hoary bat, red bat, and silver-haired bat were recorded regularly, even during summer, while tri-colored bat was positively identified at only two transects. The federally threatened northern long-eared bat was identified by Shrovnal at 18 different transects, but only after 20 July. These studies show that the coastal zone of lower Green Bay is rich in bat activity, with evidence that five and possibly a significant sixth species (northern long-eared bat) are present as local summer residents as well as migrants.
We recommend future studies to identify critical areas for lower Green Bay and Fox River bats. Both Shrovnal and Kempke found particularly high numbers at the Barkhausen Waterfowl Preserve, so this area is a strong candidate for bat conservation efforts. The bay shore area at the UW-Green Bay campus also was heavily used by bats during Shrovnal’s study. Urban Green Bay and developed suburbs are not strongly avoided by foraging bats, so the urban/suburban environment may play a significant role in bat conservation planning.
Conservation or restoration measures to improve the condition of bat populations in the LGBFR AOC include protection of large trees and cavity trees for roosting of forest bats, identification and protection of roosting sites for “cave bats” in the vicinity of the lower bay and Fox River (possibly including artificially constructed “bat houses”), and protection of known feeding areas by restricting construction of wind turbines and other potential hazards. Ongoing assessment of bat populations in the LGBFR AOC will be important to identify specific feeding areas and to follow the status of populations in light of threats by WNS syndrome and perhaps other emerging infectious diseases.
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This LGBFR AOC priority population group consists of breeding bald eagles (Haliaeetus leucocephalus) and osprey (Pandion haliaetus), two apex predators of great majestic beauty and large size. Although some individuals migrate, Bald Eagles can be found in the LGBFR AOC all year, including during the cold winter where they spend time searching for carrion and foraging over pockets of open water for fish and ducks at the De Pere Dam and near the mouth of the Fox River. Osprey migrate from their wintering grounds in the southern United States and Central America to breed in northeastern Wisconsin. Both species prefer habitats close to water, particularly Osprey since they feed almost exclusively on live fish. Bald Eagles have a more varied diet, including fish (e.g., catfish), birds (e.g., ducks), amphibians, small mammals (e.g., muskrat), and carrion (e.g., deer carcass). (Diet facts from AllAboutBirds.org).
Both species build large nests in live or dead trees that consist of large sticks, although Osprey nests are typically located at the top of the tree in more open areas while eagles place their nests near the trunk in forested settings. Eagle nests are massive: 5-6 ft in diameter and 2-4 ft tall, whereas Osprey nests are typically smaller. Although both species can build nests in natural settings, they will construct their nests on artificial nesting platforms, which is a useful tool for managers trying to encourage Bald Eagle or Osprey nests. However, because Osprey and Bald Eagles forage on similar food and nest under similar conditions, interspecific competition does occur between the two species due to aggressive and territorial behavior exhibited by Bald Eagles (Ogden 1975). Eagles are also known to steal food collected by Osprey. Care should be taken when trying to encourage Osprey to nest in an area already established by eagles. (Nesting ecology and other facts from AllAboutBirds.org).
Bald Eagles are affected by environmental toxins (Best et al. 1994, Bowerman et al. 1995, Clark et al. 1998, and others) and hence are important indicators of environmental health. Due to DDT (pesticide) effects on eggs, Bald Eagles were previously federally listed under the Endangered Species Act (ESA); however, after recovery efforts and the banning of DDT, the species rebounded and was removed from the ESA in 2007. Yet, they still suffer from lead poisoning from consuming dead carcasses shot by ammunition containing lead, collisions with vehicles, and disturbance at nest sites. Osprey experienced similar issues and declines from pesticides and DDT until they were banned. Now, Osprey face issues of their young chicks becoming entangled by fishing line, which adults use when building their nests. (Threats acquired from AllAboutBirds.org).
According to a WDNR report, 8 Bald Eagles bred in Brown County, Wisconsin in 2018, though the Wisconsin Breeding Bird Atlas II Project (WBBA2) reported roughly 4-5 nests within the LGBFR AOC boundaries during 2015-2019. Although Osprey do not currently nest in the LGBFR AOC, they have successfully nested nearby at the Izaak Walton League’s Osprey Point property in Ledgeview in 2015 (WBBA2), have tried building a nest at Bay Beach Wildlife Sanctuary in 2019 (WBBA2), and have been reported during the breeding season at multiple locations throughout the LGBFR AOC (e.g., UW-Green Bay campus, along the Fox River, Point au Sable, Barkhausen Waterfowl Preserve) according to WBBA2 and eBird records (eBird 2019).
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Coastal birds are summer resident species that use the nearshore environment for feeding or breeding, including Belted Kingfisher (Megaceryle alcyon), Green Heron (Butorides virescens), Spotted Sandpiper (Actitis macularius), and swallows (including Purple Martin [Progne subis]), Bank Swallow (Riparia riparia), and Northern Rough-winged Swallow (Stelgidopteryx serripennis). Colonial waterbirds, marsh breeding birds, and nesting Bald Eagle/Osprey, and breeding shorebirds are excluded because they are part of other fish and wildlife population groups.
This group is important because coastal birds are predators of aquatic species that depend on the coastal or nearshore environment. Swallows feed on emergent aquatic insects such as midges (Chironomidae), which may contain environmental contaminants such as polychlorinated biphenyls (PCBs), polybrominated diphenyl ether, or polycyclic aromatic hydrocarbons (Custer et al. 2017). Belted Kingfishers and Green Herons both eat fish, though Green Herons also eat anurans and a variety of invertebrates.
While the species in this group are similar in that they forage or nest in the nearshore environment, their nesting ecologies are quite different. Belted Kingfisher and Bank Swallow, for example, nest in cavities along the banks of streams or in gravel quarries or sand banks/dunes. Tree Swallows are also cavity nesters, though they typically use old woodpecker holes in live or dead trees or use nest boxes constructed by people. Northern Rough-winged Swallows build nests in old cavities or burrows created by other animals such as kingfisher, or in crevices (e.g., gutter). Cliff Swallows build open-cup mud nests under bridges, on buildings, or along natural cliffs. Purple Martins are colonial nesters and utilize artificial nest boxes with rows of openings to accommodate multiple birds. Green Herons simply build nests in trees or shrubs. (Nesting ecology facts from AllboutBirds.org).
All of the species in this group have been confirmed as breeding in or near the LGBFR AOC during the Wisconsin Breeding Bird Atlas 2 Project between 2015 and 2019 (WBBA2; eBird 2017). Along the west shore of the LGBFR AOC, all seven coastal bird species have been confirmed as breeding (e.g., through the documentation of a nest or observation of a young fledgling). Along the east shore, all but Belted Kingfisher have been documented as breeding, while all seven species are suspected to have bred along the Fox River with the exception of a confirmed Cliff Swallow nesting colony.
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The “colonial waterbirds” group refers to waterbirds that nest colonially, typically on islands or in rookeries, though site-specific nesting requirements vary. Species in the LGBFR AOC include: American White Pelican (Pelecanus erythrorhynchos), Black-crowned Night-Heron (Nycticorax nycticorax), Caspian Tern (Hydroprogne caspia), Common Tern (Sterna hirundo), Double-crested Cormorant (Phalacrocorax auritus), Great Egret (Ardea alba), Herring Gull (Larus smithsonianus), and Ring-billed Gull (Larus delawarensis). This group of birds is particularly well-studied thanks to recent long-term monitoring efforts led by Thomas Erdman, Sumner Matteson, and others at the WDNR and FWS (Qualls et al. 2013).
Because colonial waterbirds primarily eat aquatic organisms, including fish, amphibians (e.g., anurans), and aquatic macroinvertebrates, they are particularly vulnerable to bioaccumulating environmental contaminants such as pesticides, heavy metals, and PCBs, which may negatively affect reproductive success (Heinz et al. 1985, Fox et al. 1991). The importance of this population group in the LGBFR AOC was recognized early, and the original RAP stated a specific goal of maintaining self-sustaining populations of these birds (Wisconsin Department of Natural Resources 2016a).
Historically, Black-crowned Night-Herons, Great Egrets, Common Terns, Double-crested Cormorants, Herring Gulls, and Ring-billed Gulls nested on the Cat Island Chain of barrier islands that extended from the west shore of the bay of Green Bay (T. Erdman, pers. comm., Qualls et al. 2013). This island chain also protected a massive submergent/emergent marsh complex in the Duck Creek Delta, which likely provided food sources for these colonial birds. In the mid-1960s Cat Island proper was vegetated with willows and cottonwoods, making it suitable for tree-nesting colonial waterbirds (e.g., herons/egrets), though eventually the birds’ guano killed the trees (T. Erdman, pers. comm., Matteson et al. 2014). Other historic colonial nesters in lower Green Bay include Caspian Tern and Great Blue Heron; American White Pelican first nested in the lower bay in 1994 (Qualls et al. 2013, Matteson et al. 2014).
Due to extremely high water levels in the bay, massive storms, and recently hardened shorelines, most of the Cat Island Chain of islands washed away during the spring of 1973, leaving only Cat and Lone Tree Islands (Frieswyk and Zedler 2007), which persisted and are still present today. In the 1980s, a group of local conservationists proposed the bold idea of reconstructing three barrier islands, formalizing the proposal in the LGBFR AOC’s 1988 RAP. After several decades, the Cat Island Chain Restoration Site’s causeway and borders of island “cells” were constructed in May 2013. This project was enabled by a partnership between the U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, Wisconsin Department of Natural Resources, and Brown County’s Port of Green Bay Authority. A key element of the plan was the deposition of recently dredged material from the Green Bay shipping channel into the “cells” of the Cat Island Chain Restoration Site (Brown County Port and Resource Recovery Department). Over the next 20-30 years, the dredge material will continue to create the much-needed barrier island habitat for colonial nesting birds, fish, aquatic invertebrates, amphibians, migratory shorebirds, and other wildlife.
Today (2017), American White Pelican, Double-crested Cormorant, and Herring Gull nest on Cat Island proper (T. Prestby, pers. comm., eBird 2017). Nesters on Lone Tree Island include American White Pelican, Double-crested Cormorant, Black-crowned Night-Heron, Great Egret, Herring Gull, and Ring-billed Gull (T. Prestby, pers. comm., eBird 2017). Along sections of the easternmost “cell” on the Cat Island Chain Restoration Site, American White Pelican, Caspian Tern, Black-crowned Night-Heron, and Herring and Ring-billed Gulls currently nest (T. Prestby, pers. comm., eBird 2017). Just east of the mouth of the Fox River is a large Ring-billed Gull colony on the confined disposal facility (i.e., CDF), Renard Island, formerly known as Kidney Island (T. Prestby, pers. comm.). Both Ring-billed and Herring Gull populations have done extremely well in the past several years due to the introduction of invasive alewife (Alosa pseudoharengus) and rainbow smelt (Osmerus mordax; Qualls et al. 2013). Common Terns have nested on artificial platforms installed and monitored by the WDNR and U.S. Fish and Wildlife Service for the past few years. Initially, a platform was installed on the southwestern side of the westernmost “cell,” which was used by Common Terns in 2015, though the platform has since been removed. Instead, two nesting platforms were installed in between the westernmost and central “cells” and were used by Common Terns in 2016 and 2017.
Improvements may be achieved by improving nesting structures for Common Terns and possibly other species, controlling undesirable invasive plant species, enhancing the quality and extent of emergent/submergent marsh to improve food sources, and minimizing human disturbance during the nesting season. A habitat and wildlife management plan for the Cat Island Chain Restoration Site and neighboring islands will be especially important to address invasive plant species control, strategic placement of dredge material, public access restrictions, predator control, shoreline management, and balancing the needs of listed species (e.g., state endangered terns) with those that are more common (e.g., gulls).
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The “migratory landbirds” group consists of woodpeckers, cuckoos, nightjars, hummingbirds, and perching birds (Order Passeriformes) that use terrestrial habitats as migratory stopover habitat during spring or fall migration. Migratory landbirds often follow landmarks like the north-south shorelines of Green Bay, and at the end of long, daily or nightly flights they require critical habitat for refueling or resting (Diehl et al. 2003, Ewert et al. 2005, Bonter et al. 2009). Productive waterbodies like Green Bay also produce significant numbers of aquatic insects (e.g., midges [Chironomidae]) and other invertebrates, which provide much needed, protein-rich food sources for migratory landbirds (Smith et al. 1998, Bonter et al. 2009).
Although migratory landbirds are broadly abundant in the lower Green Bay coastal zone, we identify six important hotspots: 1) Point au Sable, 2) Bay Beach Wildlife Sanctuary West, 3) UW-Green Bay’s Cofrin Arboretum, including Bay Shore Woods and Beach and Mahon Woods and Creek on the east shore, 4) Ken Euers Wildlife Area, 5) Barkhausen Waterfowl Preserve, and 6) the privately-owned Malchow/Olson Tract on the west shore (Important Bird Areas, Epstein et al. 2002, Beilke 2015, eBird 2017). All of these hotspots, except the UW-Green Bay sites, are included in one of two “Important Bird Areas,” namely “Lower Green Bay Islands-Bay Beach Wildlife Sanctuary” and “Green Bay West Shore Wetlands” (Important Bird Areas webpage). These areas encompass critical migratory bird stopover habitats, such as emergent marsh, shrub carr, and both lowland and upland forest. These habitats provide refueling food sources, including fruiting shrubs and seeds in the fall and insects in the spring. Over 200 bird species have been reported at several lower Green Bay migratory landbird hotspots, though the number of species includes waterbirds, raptors, shorebirds, and other non-landbirds (eBird 2017). Because it is privately-owned, no long-term bird data are available from the Malchow/Olson Tract; however, this site comprises one of the highest quality and most diverse habitat mosaics in the LGBFR AOC coastal zone. Migratory landbirds almost certainly utilize it extensively.
Long-term research at Point au Sable by UW-Green Bay researchers has shown that this site clearly is a critical migratory landbird stopover site (Epstein et al. 2002), especially for warblers, sparrows, vireos, woodpeckers, and blackbirds (Beilke 2015). Shortly after dawn, we have witnessed migrant “fallouts” where thousands of small songbirds appear in the treetops. Presumably overnight migrants along or over Green Bay, these birds refuel along the shoreline and in or near the site’s coastal wetlands before the next leg of their journey. Point au Sable was recently listed as one of the most important sites for Rusty Blackbird (Euphagus carolinus) stopover habitat, the only site listed in the LGBFR AOC coastal zone (Beilke 2015, International Rusty Blackbird Working Group 2015). Similarly, Bay Beach Wildlife Sanctuary West has long been recognized as an important migratory stopover site, especially for warblers (Important Bird Areas webpage). Year after year, bird watchers from northeastern Wisconsin and elsewhere spend hours watching spring migrants at this site, documented by extensive records at the Cornell Laboratory of Ornithology’s eBird web site. Although the six migratory landbird hotspots support impressive concentrations of birds, migrants also use marginal, often small, habitat patches throughout the LGBFR coastal zone (e.g., Fox River Trail, suburban yards). Bird-friendly landscapes undoubtedly contribute significantly to successful bird migration throughout the region (S. Beilke and E. Giese, pers. comm., eBird 2017).
In addition to habitat loss through urbanization, woody invasive plants, such as buckthorn (e.g., glossy buckthorn, Frangula alnus) and non-native honeysuckles (Lonicera × bella), have replaced native understory plants in many forest (e.g., hardwood swamp) and shrub carr habitats. Honeysuckle fruits provide food for birds, but the nutritional value of these fruits is poorer than that of native species like Cornus spp., Amelanchier spp., and Prunus spp. (Ewert and Hamas 1995, Smith et al. 2013). Likewise, Oguchi et al. (2017) found that birds in migratory stopover habitats dominated by invasive fruit-bearing shrubs and trees had poorer immune status and lower immunostimulatory antioxidants than conspecifics in habitats dominated by native shrubs and trees. Davis (2011) argued that non-native species pose little or no threat to migratory birds, but this conclusion is based mainly on the quantity rather than the quality of food for migrants.
Planting native shrubs (e.g., cherry [Prunus spp.], dogwood [Cornus spp.], grape [Vitis riparia]) in urban parks and degraded woodlands will increase the availability of quality, nutritional fruits for migrant landbirds, especially during August, September, and October (Drummond 2005). Other steps to improve the condition of migrant landbird populations include 1) encouraging native landscaping in backyards and commercial grounds, 2) conserving hardwood swamps, which provide abundant insects and resting habitat for long-distance migrants, and 3) improving all types of natural habitats in the lower Green Bay coastal zone, especially along shorelines.
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The “marsh breeding birds” group consists of birds regularly encountered in emergent marshes, including marsh-obligates and several marsh-users, but excluding wetland-breeding terns (e.g., Black Tern [Chlidonias niger]) and other species (e.g., coastal bird [breeding season], Osprey), which are treated separately. A marsh-obligate is a bird species that only breeds and lives in open marshes and not any other habitat, including species such as American Coot (Fulica americana), Yellow-headed Blackbird (Xanthocephalus xanthocephalus), Virginia Rail (Rallus limicola), Marsh Wren (Cistothorus palustris), Least Bittern (Ixobrychus exilis), and others. In contrast, a marsh-user is a species that may use marshes for foraging and breeding but does not necessarily require open, emergent marshes for breeding (e.g., Common Yellowthroat [Geothlypis trichas], Red-winged Blackbird [Agelaius phoeniceus], Song Sparrow [Melospiza melodia], Blue-winged Teal [Anas discors], and others. Common Yellowthoat, for example, will breed in open wetlands, grassy areas, shrub carr, and forests (Guzy and Ritchison 1999).
Within the LGBFR AOC, marsh breeding birds use high energy coastal, inland, riparian, and roadside emergent marshes, though some bird species are more sensitive to disturbed marsh areas than others (Howe et al. 2007, Gnass Giese et al. 2018). Sandhill Crane (Grus canadensis) and Swamp Sparrow (Melospiza georgiana), for example, tend to be found in higher quality emergent marshes (Howe et al. 2007); whereas, Red-winged Blackbirds are known to breed in heavily disturbed, emergent roadside marshes along major highways and interstates (Wisconsin Breeding Bird Atlas 2 Project; eBird 2017).
Different marsh breeding bird species utilize a variety of local habitats within emergent marshes. For example, Yellow-headed Blackbirds build nests over water in wetter habitats, such as cattail-dominated (Typha spp.) marshes, while American Bitterns (Botaurus lentiginosus) nest in drier habitats like grassy emergent plants (Twedt and Crawford 1995, Lowther et al. 2009, Gnass Giese et al. 2018). Still others (e.g., American Coot) nest on floating mats of dead vegetation (Brisbin Jr. and Mowbray 2002). The marsh breeding bird group is also highly affected by changing water levels in the Great Lakes, at least in coastal emergent marshes, which are affected by seiche and storms (Timmermans et al. 2008, Gnass Giese et al. 2018). Species, such as Sandhill Crane, Swamp Sparrow, and Sedge Wren (Cistothorus platensis), are associated with lower water levels, while, Marsh Wren, Pied-billed Grebe (Podilymbus podiceps), Sora (Porzana carolina), and American Coot are more commonly found during higher lake levels (Timmermans et al. 2008, Gnass Giese et al. 2018). Generally, more bird species are present in Green Bay emergent marshes during higher water levels, perhaps due to the more favorable ratio of open water to emergent marsh vegetation (Gnass Giese et al. 2018).
According to our observations and 2014-2017 data from the Wisconsin Breeding Bird Atlas 2 and local experts (e.g., T. Prestby, pers. comm.), many important marsh breeding birds currently nest in the LGBFR AOC, especially at Peters Marsh, the Duck Creek area, Dead Horse Bay / Longtail Point, and Point Sable (Table 2.6). Multiple records of Sandhill Crane, Yellow-headed Blackbird, and American Coot breeding in the LGBFR AOC have been confirmed, but only one recent breeding record has been confirmed for American Bittern, Gadwall (which was abundant historically), Least Bittern, and Virginia Rail (eBird 2017). Presently, no breeding records have been documented for Sedge Wren and Wilson’s Snipe, although observers have reported several “probable” breeding records, where an observer witnessed an adult being agitated (perhaps near a nest or young) or giving a courtship display (eBird 2017). The absence of Sedge Wren breeding records is significant, though not surprising, since less than 1 ha of southern sedge meadow habitat remains within 1 km inland of the LGBFR AOC boundary. At well over 20-30 locations, common marsh-users, such as Red-winged Blackbird and Mallard, have been regularly reported breeding in the LGBFR AOC (eBird 2017). Undoubtedly more breeding records will be noted in the LGBFR AOC during the remaining two years of the Wisconsin Breeding Bird Atlas 2 Project.
Bay Beach Wildlife Sanctuary West/East and Point Sable belong to the Lower Green Bay Islands-Bay Beach Wildlife Sanctuary Important Bird Area (IBA; Important Bird Areas webpage). The Duck Creek Delta and entire west shore belong to the Green Bay West Shore Wetlands IBA, which was identified for its importance of providing marsh bird nesting habitat (Important Bird Areas webpage). Although degraded by invasive species and other impacts, these areas continue to provide some of the most significant wildlife habitat in the LGBFR AOC.
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The population group “breeding shorebirds” includes two common breeders in the LGBFR AOC, namely Killdeer (Charadrius vociferus) and Spotted Sandpiper (Actitis macularius), as well as any other potential rare breeders, such as Piping Plover (Charadrius melodus) and Wilson's Phalarope (Phalaropus tricolor). Virtually all other shorebirds that occur in the LGBFR AOC migrate through the area using it as stopover habitat as they head north to breed in the Arctic regions. They tend to forage and nest along nearshore and coastal environments with a diet largely consisting of invertebrates, including insects, spiders, worms, aquatic larvae, etc.
Killdeer create nesting scrapes on substrates consisting of sand or gravel (including parking lots) that are generally open with some to no grassy vegetation but not necessarily near water. Like Killdeer, the Piping Plover also creates a scrape or indentation in sand or gravel but prefers to be in close proximity to water in remote, undisturbed locations with almost no vegetation. Piping Plover is a federally endangered species due to habitat loss from a lack of undisturbed beaches, which have been lost due to shoreline development and recreational beach activities. Spotted Sandpipers nest close to water and create a scrape in soil, sand, or gravel under the shade of a plant (e.g., tree sapling, raspberries). Wilson’s Phalaropes nest near wetlands or water and create a scrape in the ground surrounded by vegetation. (Nesting ecology facts from AllAboutBirds.org). Young chicks of these four shorebirds are precocial at birth meaning within hours of hatching, they get up and feed on their own under the watchful eye of their parents. Because all of these breeding shorebird species nest on the ground and in some cases on wide open exposed substrate, they can be particularly vulnerable to predators, including coyotes, owls, cats, gulls, raccoons, Peregrine Falcons, and others.
According to the Wisconsin Breeding Bird Atlas II Project (2015-2019), the following species bred at each of the Cat Island Wave Barrier (Killdeer, Spotted Sandpiper, Piping Plover, and Wilson’s Phalarope), Longtail Point (Spotted Sandpiper), and Point au Sable (no breeding confirmations of any of these shorebird species). Killdeer and Spotted Sandpiper nested at several other locations in the LGBFR AOC. In the future, Killdeer and Spotted Sandpiper would almost certainly nest at Point au Sable (since they have in the past), Piping Plover (under the right conditions) might nest at Longtail Point or Point au Sable, and another rare breeding shorebird might nest at a site in the LGBFR AOC. Piping Plovers nesting at the Cat Island Wave Barrier in 2016 was a momentous event having been the first time in over 75 years. A pair of Wilson’s Phalaropes also nested at Cat Island, which represented one of the only nesting confirmations in the state. It is clear that lower Green Bay is an important stronghold for nesting shorebirds. After the summer nesting season, each species migrates south to warmer climates where food is plentiful to spend the winter, including the southern United States, Caribbean, and Central and South America.
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The “shorebirds (migratory)” species group consists of approximately 25 shorebirds (Order Charadriiformes) that regularly use shoreline, coastal, and wetland habitats in the LGBFR AOC as stopover habitat during spring or fall migration. This group includes plovers, sandpipers, godwits, dowitchers, yellowlegs, phalaropes, and other subgroups. Major stopover habitats for migratory shorebirds are mud flats, Great Lakes beach, rocky shorelines, open wetlands, shallow waters along the coastline, grasslands, and even flooded agricultural lands in the coastal zone (Helmers 1992, de Szalay et al. 2000). Peak migratory concentrations in lower Green Bay usually occur from late May through early June (spring migration) and August through September (fall migration), although fall migrants (usually post-breeding adults) begin to appear as early as mid-July, and some shorebirds persist well into October (Prestby 2015). Most migratory North American shorebirds breed in arctic or sub-arctic regions of northern Canada and Alaska and winter along the coast or wetlands of Central America, the southern United States, or Mexico.
Great Lakes coastal areas provide critical stopover habitat for shorebirds traveling through the interior of North America after long, often non-stop flights from wintering or breeding grounds (Diehl et al. 2003). The lower Green Bay coastal zone provides protein-rich food sources, such as aquatic insects, worms, snails, midges, and other invertebrates (Helmers 1992). Depending on shorebird species, body shape, and bill size, different species forage for food using different techniques. Plovers, for example, are terrestrial/aquatic gleaners, which means that they glean or pick up food along the habitat they are using (Helmers 1992). Aquatic probers, like godwits, use their bills to probe food from mud or sand substrates (Helmers 1992). Migratory shorebirds are important because they are predators of aquatic species that depend on the coastal or nearshore environment, which may contain environmental contaminants such as pesticides, heavy metals, and polychlorinated biphenyls (PCBs; Qualls et al. 2013, Russell et al. 2016).
The importance of lower Green Bay as a stopover site for shorebirds was recognized by Potter et al. (2007), but more recently Prestby (2015) has documented an extraordinary and diverse migration of shorebirds at the Cat Island Chain Restoration Site, which was constructed to restore the historical Cat Island Chain of barrier islands. The Cat Island Chain Restoration Site is located within the Green Bay West Shore Wetlands Important Bird Area (Important Bird Areas webpage) near Peters Marsh on the west shore of Green Bay. Public access to this site is prohibited for the protection of wildlife and because it is an active construction site. While migratory shorebirds use other stretches of undeveloped Great Lakes beach, wetlands, and natural habitats in the LGBFR AOC, we identify just two important migratory shorebird hotspots: the Cat Island Chain Restoration Site and Point au Sable (T. Prestby, pers. comm.), which includes more than 2 km of undeveloped beach habitat. Historically, three large barrier islands comprised the Cat Island Chain, providing critical fish and wildlife habitat off the west shore of the lower bay. However, due to unusually high water levels, massive storms, and hardened shorelines, nearly all of these islands washed away during a storm event during the spring of 1973. In the 1988 RAP, a group of local conservationists proposed the idea of reconstructing these islands (Wisconsin Department of Natural Resources 2016a). The idea materialized >20 years later. By May 2013, the Cat Island Chain Restoration Site and framework of three island “cells” were constructed. Two of the “cells” have been filled with some dredge material from the Port of Green Bay shipping channel. Over the next 20-30 years, additional dredge material will be added to each of the three “cells.” So far, the dredge material deposited in the westernmost “cell” has largely consisted of sand, silt, and clay, which has in turn created excellent shorebird habitat. Thomas Prestby’s (2015) master thesis provided a baseline study of migratory shorebirds in the lower bay, perfectly timed to coincide with the construction of the Cat Island Chain Restoration Site. He documented >30 species of shorebirds at the Cat Island Chain Restoration Site between 2013 and 2014. In fact, Prestby’s (2015) study showed that the Cat Island Chain Restoration Site is the most important and diverse migratory shorebird stopover location in the entire state of Wisconsin (eBird 2017). Migrant shorebirds that use the barrier relatively frequently include Black-bellied Plover (Pluvialis squatarola), Semipalmated Plover (Charadrius semipalmatus), Ruddy Turnstone (Arenaria interpres), Sanderling (Calidris alba), Baird’s Sandpiper (Calidris bairdii), Least Sandpiper (Calidris minutilla), Pectoral Sandpiper (Calidris melanotos), Semipalmated Sandpiper (Calidris pusilla), Greater Yellowlegs (Tringa melanoleuca), and Lesser Yellowlegs (Tringa flavipes; eBird 2017, Prestby 2015).
Especially during lower water years, Point au Sable provides important migratory shorebird stopover habitat along the east shore of the bay. Foraging habitat for shorebirds occurs on the outer perimeter of the peninsula (Great Lakes beach) and in wet, muddy areas along the edges of the inner lagoon. Point au Sable is located within the designated Lower Green Bay Islands-Bay Beach Wildlife Sanctuary Important Bird Area (Important Bird Areas webpage). At Point Sable, Prestby (2015) reported Greater Yellowlegs, Lesser Yellowlegs, Ruddy Turnstone, Dunlin, Least Sandpiper, and several other species.
Changing water levels in the bay can greatly impact the number and types of shorebirds that migrate through the LGBFR AOC. Stopover locations with mud and exposed shoreline that are available to shorebirds on one day may become flooded days or weeks later if water levels rise along the coastal zone (Ewert et al. 2005, Potter et al. 2007, Prestby 2015). The same is true of temporarily flooded agricultural fields, which often dry quickly due to drain tiles or soil infiltration. Controlling water levels in diked wetlands or strategically timing the deposition of dredge material in the “cells” of the Cat Island Chain Restoration Site, for example, can help provide reliable stopover habitat for migrant shorebirds (Ewert et al. 2005, Prestby 2015). Maintaining gradually-sloped mudflats in the recently placed dredge material in the Cat Island Chain Restoration Site “cells” will maximize the amount of stopover habitat for shorebirds across different water levels (Prestby 2015).
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Migratory ducks, geese, and swans comprise one of the most visible and economically important species groups in the LGBFR AOC. Prince et al. (1992) recognized Green Bay as one of 15 concentration areas for migratory waterfowl in the Great Lakes and by far the most heavily used site in Lake Michigan for diving ducks and sea ducks. Harris (1998) found that numbers of diving ducks increased after invasion of non-native dreissenid mussels between 1977-78 and 1994-97. This result is consistent with studies by Mazak et al. (1997), Badzinski and Petrie (2006), and Schummer et al. (2010), who showed that dreissenids are major components in the diets of scaup (Aythya spp.) and other divers in the Great Lakes.
The northeast-southwest orientation of Green Bay creates a natural landmark for migrants, and the shallow, lower bay supports productive waterfowl food resources, even though it has been highly modified by pollution and invasive species. Submerged aquatic vegetation, abundant aquatic macroinvertebrates (particularly dreissenid mussels), and a rich and productive fish community attract tens of thousands of diving ducks in the lower bay, creating a “destination” for birdwatchers and hunters.
During 2016-17 we enlisted Thomas Prestby to conduct a shore-based survey of waterfowl from eight strategic locations in in the LGBFR AOC and two localities (Sensiba Wildlife Area and Bay Shore County Park) just north of the LGBFR AOC. During 263 counts on 30 survey days, he recorded 28 species of waterfowl (15 diving ducks, 9 marsh ducks, 2 geese, and 2 swans). Waterfowl rafts were counted and mapped during each survey.
Fall migration begins in Great Lakes coastal marshes during late August, when Blue-winged Teal (Anas discors) assemble in migratory flocks (Soulliere et al. 2007) prior to their departure in late September. Our surveys did not begin until October 12th, but numbers of Blue-winged Teal in the lower bay were not high during the corresponding spring migration period in 2017. Other marsh ducks including Wood Duck (Aix sponsa), Northern Pintail (Anas acuta), Gadwall (Anas strepera), Northern Shoveler (Anas clypeata), American Wigeon (Anas americana), Mallard (Anas platyrhynchos), American Black Duck (Anas rubripes), and Green-winged Teal (Anas crecca) occur in modest numbers during October, but the lower bay does not appear to be a major stopover site for these species. By far the highest numbers were recorded for Mallards, which were abundant winter residents in open water areas at the mouth of the Fox River and below the De Pere Dam. The high count for a single day during winter was 5,491 Mallards on 10 December 2016. Aside from Mallards, the most commonly observed marsh ducks in the LGBFR AOC during migration were (in decreasing order of abundance) Gadwall, American Wigeon, Northern Pintail, Green-winged Teal, Northern Shoveler, and American Black Duck.
Canada Geese (Branta canadensis) were always present in the lower bay, reaching daily peak numbers of over 500 individuals during early November and continuing at high numbers through the winter. By mid-April, fewer than 100 Canada Geese were recorded on individual days, presumably because pairs had either departed the area or had dispersed to local breeding sites. Tundra Swans (Cygnus columbianus) were observed in the lower bay during late Marsh and early April 2017, with the largest recorded flock of 151 individuals on 22 March 2017. Other noteworthy migratory waterbirds included American Coot (Fulica americana; flocks of 500-600+ observed along the Cat Island Wave Barrier and Long Tail Point during November 2016), two regularly seen species of grebes (Pied-billed [Podilymbus podiceps] and Horned Grebe [Podiceps auritus]), Common Loon (Gavia immer; especially along east shore), Red-throated Loon (Gavia stellata), and several rare species recorded on just one or two dates (Trumpeter Swan [Cygnus buccinator], Pacific Loon [Gavia pacifica], Red-necked Grebe [Podiceps grisegena], Eared Grebe [Podiceps nigricollis]).
By far the greatest numbers of waterfowl were diving ducks, especially Greater (Aythya marila) and Lesser Scaup (Aythya affinis), Common Goldeneye (Bucephala clangula), Common Merganser (Mergus merganser), and Red-breasted Merganser (Mergus serrator). The maximum number of diving ducks (including mergansers) recorded during a single day was 58,448 individuals on 5 March 2017, but Prestby typically estimated more than 10,000 divers on days during late November and early December 2016 and from early March through late April 2017. Even less abundant species like Ruddy Duck (Oxyura jamaicensis; maximum 3,236 individuals on 15 April 2017), Redhead (Aythya americana; 3,980 individuals on 3 April 2017), Canvasback (Aythya valisineria; 2,550 individuals on 3 April 2017), Long-tailed Duck (Clangula hyemalis; 793 individuals on 10 May 2017), Ring-necked Duck (Aythya collaris; 406 individuals on 9 April 2017), and Bufflehead (Bucephala albeola; 203 individuals on 11 November 2016) were well represented.
As long as open water was present, diving ducks (and Mallards) were present in large numbers during 2016-2017. During winter all ducks were concentrated below the De Pere Dam or in open water at the mouth of the Fox River. By late February some open water appeared off the Cat Island Wave Barrier in the Green Bay shipping channel, and by late March open water was widespread. Once open water was present throughout the lower bay, the largest numbers of diving ducks were recorded from the east shore. This pattern was true during both fall and spring. Large numbers of divers also were recorded on the west shore during this time, however. The importance of the De Pere Dam and the mouth of the Fox River diminished significantly in late spring and fall (before ice), perhaps due in part to heavy traffic by recreational fishing boats.
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Forster’s Tern (Sterna forsteri) and Black Tern (Chlidonias niger), comprising the “wetland terns” group, are summer resident bird species that breed in wetlands and forage nearby in wetlands and other nearshore habitats, especially emergent/submergent marshes and open water. Threats from habitat loss (e.g., wetland filling, development), invasive species, and bioaccumulation of polychlorinated biphenyls (PCBs) and other toxins have led to both species being listed as state endangered, and Black Tern also is a federal species of concern (Mossman 1989, Qualls et al. 2013). Both species nest in large, extensive emergent marshes (inland and coastal) that are relatively free from human disturbance and human-associated predators (Mossman 1989, McNicholl et al. 2001, Heath et al. 2009). Wetland terns typically build nests on floating mats of dead vegetation in deep water, but individuals also use muskrat lodges and artificial nesting platforms (McNicholl et al. 2001, Heath et al. 2009).
Wetland terns are sensitive to both habitat and water quality stressors. Both species are predators of fish and aquatic macroinvertebrates in the coastal or nearshore environment. These prey items can bioaccumulate environmental contaminants such as pesticides, heavy metals, and PCBs, which are further concentrated in tissues of their predators. Forster’s Terns primarily eat small fish, though Black Terns eat odonates, mayflies, crayfish, and small fish (McNicholl et al. 2001, Heath et al. 2009). Harris et al. (1985) and Harris et al. (1993) found that environmental contaminants negatively affected Forster’s Terns reproductive success in Green Bay and the Fox River watershed (McNicholl et al. 2001); in addition to direct effects, pesticides may contribute to declines in numbers of Black Terns’ preferred invertebrate prey (Heath et al. 2009).
Historically, both wetland terns bred in large numbers in the LGBFR AOC (Mossman 1989, T. Erdman pers. comm.). In fact, the Green Bay Black Tern colony was the largest in the state in the early 1980s (Qualls et al. 2013). Historically, they nested at sites such as the Pulliam Plant/Tank Farm area, Ken Euers Nature Preserve, and Grassy Island (T. Erdman, pers. comm.), in addition to a nearby breeding colony in Suamico (Cutright et al. 2006). More recently, Black Terns have declined alarmingly between the 1980s and 2000s (Matteson et al. 2012) and no longer nest regularly in the LGBFR AOC. Despite the WDNR’s efforts to install artificial nesting platforms for Black Terns at Dead Horse Bay/Longtail Point in 2017, no nests or recently fledged young have been found within the past few years; however, biologists witnessed agitated behavior of Black Terns (i.e., adults aggressively diving at biologists) at Dead Horse Bay/Longtail Point in 2016 and 2017 (eBird 2017); agitated tern behavior can signify that a nest or young is nearby, though it is not enough evidence to confirm breeding activity.
During the late 1960s through late 1980s, Forster’s Terns nested at several locations in lower Green Bay, including Point au Sable, Duck Creek Delta, Longtail Point, Renard Island (formerly known as “Kidney Island”), Pulliam Plant/Tank Farm area, Ken Euers Nature Preserve, and Sensiba State Wildlife Area just north of Longtail Point, but outside of LGBFR AOC study area (Mossman 1989, T. Erdman, pers. comm.). According to records from the first Wisconsin Breeding Bird Atlas Project (WBBA), Forster’s Terns bred in the LGBFR AOC between 1995 and 1997 (eBird 2017). The WDNR recently installed artificial nesting platforms for Forster’s Terns in the LGBFR AOC. These have been used successfully by Forster’s Terns in 2017 near the Cat Island Chain Restoration Site (2015 only), Duck Creek Delta, and Dead Horse Bay/Longtail Point (J. Martinez, pers. comm.). For now, the WDNR will continue maintaining the Duck Creek and Dead Horse Bay nesting structures, though not the one at the Cat Island Chain Restoration Site, where the platform was converted in 2017 for Common Tern (Sterna hirundo) usage (J. Martinez, pers. comm.).
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The “wooded wetland birds (breeding)” species group consists of birds that breed in hardwood swamps, which includes forest-dwelling woodpeckers, vireos, flycatchers, cuckoos, nuthatches, thrushes, warblers, and a few other species, as well as shrub carr-affiliated species. To identify species that use wooded wetlands or shrub carr for nesting, we compiled lists provided by Fowler and Howe (1987), Hoffman and Mossman (1993), and Hoffman (1989) as well as species accounts provided by the Cornell Lab of Ornithology’s Birds of North American Online and the “All About Birds” webpage. These sources were not restricted to lower Green Bay, however, so we excluded some of the listed species that were out of range, typically breed in non-wooded wetland habitats, were non-native (e.g., Ring-necked Pheasant [Phasianus colchicus]), or were more closely associated with people (e.g., American Robin [Turdus migratorius]). We also identified which hardwood swamp- and shrub carr-affiliated bird species currently nest in the LGBFR AOC using data provided by the Wisconsin Breeding Bird Atlas 2 Project (eBird 2017). Some species that we have identified as wooded wetland breeders do not necessarily exclusively breed in hardwood swamps or shrub carr. In fact, many species use other habitats (e.g., Blue Jay, Ovenbird).
Because this population group is rather large and diverse, the needs of each species vary for appropriate nesting and foraging habitats. Flycatchers, such as Eastern Wood-Pewee, need open gaps in the forested wetlands with adequate perches used for catching insects “on the wing,” while birds, such as Wood Thrush, prefer interior forest with little edge (Hoover et al. 1995). Woodpeckers and nuthatches search for food and excavate cavities for nesting in dead trees, rotting wood, hollowed out trees, and snags. Broad-winged Hawks prefer younger forests with openings for breeding (Goodrich et al. 2014), unlike Red-shouldered Hawks, which seek more mature forest stands (Dykstra et al. 2008). Hardwood swamp micro-habitats created by fallen logs, coarse woody debris, and snags are preferential to species like Winter Wren (Hejl et al. 2002). Dense leaf litter along the forest floor is used by Ovenbirds and Veeries both for foraging for insects (e.g., ants) and nest building (Hoover et al. 1995, Porneluzi et al. 2011, Heckscher et al. 2017). All these features are present in mature hardwood swamps that experience the natural disturbance regime typical of forests in the western Great Lakes.
Historically, little has been published about wooded wetland breeding birds in northeastern Wisconsin. However, the west shore was largely covered by swamp conifer forest (1840s PLSS records from the WDNR Surface Water Data Viewer) with black spruce (Picea mariana) and balsam fir (Abies balsamea; T. Erdman, pers. comm.), so it is likely that birds of northern wet mesic forest habitat were more abundant, diverse, and widespread than they are today in the LGBFR AOC. During the 1800s and early 1900s, a significant amount of Wisconsin’s forests was heavily logged and have since been converted to farmland, development, and early successional forests dominated by Populus spp. and other pioneer tree species (Frelich 1995). The original RAP states the importance of having “a balance of diverse habitat types exist within the AOC that supports all life stage requirements of fish and wildlife populations including multiple wetland types (for example: …forested and shrub…)” (Wisconsin Department of Natural Resources 2016a). The document also stresses the need for having “populations of traditionally harvested wildlife species,” which includes wooded wetland breeder, Ruffed Grouse, and shrub-forest breeder, American Woodcock (Wisconsin Department of Natural Resources 2016a).
According to 2015-2017 data from the Wisconsin Breeding Bird Atlas 2 Project, many important wooded wetland breeding birds currently nest in the LGBFR AOC, especially at Barkhausen Waterfowl Preserve, Cottage Grove Complex, Point Sable, Bay Beach Wildlife Sanctuary West, and Peters Marsh (Tables X and Y). Multiple confirmed breeding records have been reported for forest-dwelling species Baltimore Oriole (9), Black-capped Chickadee (8), Gray Catbird (6), Northern Flicker (6), Blue Jay (5), and Downy Woodpecker (5) and shrub carr-affiliated species Cedar Waxwing (6), Yellow Warbler (6), American Goldfinch (5), and Song Sparrow (5; eBird 2017). Presently, no confirmed breeding records have been reported in the LGBFR AOC for Black-billed Cuckoo, Broad-winged Hawk, Brown Creeper, Mourning Warbler, Northern Waterthrush, Ovenbird, Red-breasted Nuthatch, Red-eyed Vireo, Ruffed Grouse, Scarlet Tanager, Winter Wren, Yellow-billed Cuckoo, and Alder Flycatcher, except for “probable” (e.g., agitated adult, courtship display) or “possible” (e.g., singing male) breeding records (eBird 2017); however, Alder Flycatcher more frequently use alder thickets in northern Wisconsin. Black-and-white Warbler and Red-shouldered Hawk were not reported at all during the breeding season in the LGBFR AOC, though they do use forested wetlands in this region for breeding. However, two more years are left in the Wisconsin Breeding Bird Atlas 2 Project; undoubtedly additional breeding records will be noted in the future in the LGBFR AOC.
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Despite more than a century of agricultural, municipal, and industrial pollution, the seven miles of the lower Fox River from the De Pere Dam to the waters of Green Bay today support one of the most productive recreational fisheries in Wisconsin and probably in the entire western Great Lakes region.
The “Fox River fish” group includes fish species that use the Fox River north of the De pere dam as residents, seasonal migrants, or for development during critical life stages, including but not limited to: sunfishes and basses (Centrarchidae), channel catfish (Ictalurus punctatus), lake whitefish (Coregonus clupeaformis), lake sturgeon (Acipenser fulvescens), walleye (Sander vitreus), etc. Lake sturgeon is a state-listed special concern species and is considered “vulnerable” in the state (S3 rank).
Walleye tend to be associated with large lakes and rivers, such as the Fox River, and are mainly bottom dwellers, spending time in deep waters during the day and foraging near the surface at dusk. They feed on bullhead (Ameiurus spp.), yellow perch (Perca flavescens), minnows, crayfish, aquatic worms, and other small prey items (Mecozzi’s walleye fact sheet). They spawn in waters between 0.5 m and 3 m deep with reefs or shoreline rock, including downstream of the De Pere Dam in the Fox River (S. Hogler, pers. comm.). Young juvenile/fingerling walleye utilize open water and shoreline areas, while adults primarily use the open waters of large rivers and lakes (S. Hogler, pers. comm.). During the early 1900s, walleye populations in lower Green Bay were nearly extirpated because of water pollution, over-fishing, and habitat destruction; however, WDNR biologists’ fry and fingerling stocking efforts in the 1970s and 1980s in the Fox River just south of the Mason Street Bridge has significantly helped walleye populations recover to the point that they are now self-sustaining (Qualls et al. 2013, Hogler et al. 2015). Restored walleye spawning areas (e.g., reefs) are located at Voyageur Park, Ashwaubomay Memorial River Park, and Fox Point Boat Launch.
Lake sturgeon are found in large rivers and glacial lakes of North America from the Mississippi River to Hudson Bay (Becker 1983). Along the bottom of rivers or lakes, they feed on small invertebrates, such as snails, leeches, and insects, using suction since they lack teeth (Lake Sturgeon Webpages). They need rocks and warm waters (11.7-15°C [53-59°F]) for spawning with adequate stream flow and regularly spawn below the De Pere Dam on the Fox River (S. Hogler, pers. comm., Lake Sturgeon Webpages). Juveniles tend to use rivers, mouths of rivers, and muddy and silty areas, while adults use large rivers, open water, and shorelines (S. Hogler, pers. comm.). During the early 1900s, lake sturgeon populations in Lake Michigan rivers significantly declined due to overharvesting, poor water quality, and fish passage barriers, though currently their populations are relatively self-sustaining through conservation efforts (Donofrio et al. 2015).
Lake whitefish adults and juveniles are bottom dwellers in open-water habitats, where they stay as deep as ~100 m during the daytime and then move to shallower waters at night where they eat invertebrates and small fish (S. Hogler, pers. comm., Lake Whitefish, University of Wisconsin Sea Grant Species Account). They prefer to spawn along shorelines with rock, including downstream of the De Pere Dam in the Fox River (S. Hogler, pers. comm.). Historically, huge numbers of lake whitefish once inhabited the Great Lakes; however, their populations were decimated during the twentieth century due to overharvesting and the destruction of important spawning areas by the lumber industry (Lake Whitefish University of Wisconsin Sea Grant Species Account, Qualls et al. 2013). Their preferred prey, Diporeia (zooplankton), largely vanished with the arrival of zebra/quagga mussels (Dreissena spp.; Lake Whitefish University of Wisconsin Sea Grant Species Account). Once water quality improved, lake whitefish returned to the Fox River and other rivers roughly 10-15 years ago, after being absent for over 100 years (Qualls et al. 2013, S. Hansen as reported in Parr 2016).
Adult channel catfish use open water and rivers, including the Fox River, where they favor deep holes and woody debris. Juveniles tend to use a broader variety of microhabitats in rivers (S. Hogler, pers. comm.). Like the other Fox River Fish species, catfish are bottom dwellers and are most active at night in shallow waters (Catfish Fact Sheet). Adult channel catfish diet is broad since they are mostly opportunistic scavengers and may consume small fish, crayfish, carrion, and snails (Catfish Fact Sheet, Wisconsin Department of Natural Resources 2016c). Channel catfish typically build nests along undeveloped shorelines (S. Hogler, pers. comm.) and spawn in the Fox River, though not at the De Pere Dam. They are relatively tolerant to turbid waters, though individuals prefer clearer, slower waterways (Catfish Fact Sheet). Historically, catfish were regularly caught by early fishermen in the late 1880s (Qualls et al. 2013).
Many fish species, including those in the Fox River fish group, were originally listed in the RAP because of poor quality spawning habitat, impaired reproduction, low overall fish diversity, poor water quality, fish passage barriers, and introduction of invasive species such as zebra/quagga mussel and sea lamprey; Qualls et al. 2013, Wisconsin Department of Natural Resources 2016a). Fox River fish are good indicators of ecological condition in the LGBFR AOC because they consume prey that depend on the coastal or nearshore environment, which may contain environmental contaminants such as polychlorinated biphenyls (PCBs) and mercury (Catfish Fact Sheet, Qualls et al. 2013). Predators higher in the food chain that consume Fox River fish species (including people) are vulnerable to bioaccumulation of these organic toxins, which can cause reproductive issues or deformities (Qualls et al. 2013). Today, fish advisories recommending safe fish consumption by species are regularly posted at boat launches and parks along the Fox River.
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The “shoreline fish” group, which consists of 25 species inhabiting shoreline areas and shallow open water. Most species in this group spawn along vegetated, sandy, or rocky shorelines, although species like spotfin shiner (Notropis spilopterus) require other habitats like crevices or bark of submerged logs (Gale and Gale 1977). Many species on this list use tributaries as breeding or nursery habitat, but all of them have been collected along shorelines of the lower bay (Brazner and Beals 1997, Koosmann 2016).
Shoreline fish along sandy beaches are typically distinct from those of coastal wetlands, although the difference is much less pronounced in lower Green Bay than in the middle or upper bay (Brazner and Beals 1997). Even in the upper bay, some shoreline species occur in both sandy beaches and wetlands, so we combine the two groups of shoreline fish for assessment metrics, recognizing that management recommendations will be different for beach vs. wetland shorelines.
Brown County records from 1885 describe a wide diversity of native fish in Green Bay, including perch, muskellunge, sunfish, crappies, suckers, catfish, and many others (Smith and Snell 1891, Qualls et al. 2013). Many of the fish species described in this early account are still represented in the LGBFR AOC, although invasive species and habitat modifications have changed the shoreline fish community irreversibly. Here we describe four native taxa (smallmouth bass, muskellunge, yellow perch, and shoreline/wetland Centrachidae) that have historical, ecological, and economic importance in this ecosystem. Other species included in our assessment metric represent a broader fish diversity in the shoreline zone, in some cases overlapping with species in the tributary fish category.
Turbidity, submerged aquatic vegetation, and substrate conditions all affect the success of shoreline fish. Smallmouth bass inhabit shorelines that have rock, gravel, and submerged logs (S. Hogler, pers. comm., Michigan Department of Natural Resources 2018b). Young fry eat benthic invertebrates, including dreissenid mussels, while adults feed almost exclusively on round gobies (Nelson et al. 2017). Smallmouth bass spawn along shallow shorelines, ~0-2 m deep, that consist of gravel, sand, cobble, bedrock, and logs with little to no vegetation and even near boat docks (Lane et al. 1996, S. Hogler, pers. comm.). Adult males build gravel nests along the shoreline near deeper waters for refuge. They guard the nest and young fry for many days after hatching (Michigan Department of Natural Resources 2018b). Like other nearshore breeders, individuals must protect their eggs against round gobies and other potential predators (Qualls et al. 2013). Smallmouth bass use the pelagic zone of the lower bay, including Point Sable and UW-Green Bay campus shoreline, Fox River, and upper Duck Creek (Lower Green Bay and Fox River Area of Concern Biota Database, Wisconsin Department of Natural Resources Fish Mapping Application 2018).
Great Lakes muskellunge, also known as simply muskellunge or Great Lakes/spotted musky, is perhaps the most important game fish in the state. This species was designated the state fish in 1955 (Simonson 2015). Muskellunge can grow to 1.3 m long, weigh up to 31.8 kg, live for over 30 years, and are highly prized by local fishermen (Simonson 2015). Great Lakes muskellunge use open water habitats, including both deep and shallow waters. They are known to use submerged aquatic vegetation, especially several wide-leaved species of native pondweed (Potamogeton spp.; Simonson 2015). Individuals prefer clear, less turbid waters for visibility while hunting (Wisconsin Department of Natural Resources Muskellunge Fact Sheet). Adult muskies are opportunistic, ambush predators at the top of the food chain. They hide amongst vegetation and rocks waiting for prey, primarily consisting of suckers, yellow perch, and minnows. Individuals also have been reported consuming crappies, ducks, mice, anurans, and even muskrats (Simonson 2015, Wisconsin Department of Natural Resources Muskellunge Fact Sheet). Great Lakes muskellunge spawn along hundreds of meters of shoreline with shallow waters (0-2 m deep) that consists of silt, clay, gravel, and sand with submergent and emergent vegetation (e.g., bulrush) and or woody debris (Lane et al. 1996, Simonson 2015, S. Hogler, pers. comm.). They have recently been reported using the Fox River and open water of the lower bay including Dead Horse Bay (Lower Green Bay and Fox River Area of Concern Biota Database, Wisconsin Department of Natural Resources Fish Mapping Application 2018). Since 2000, WDNR’s Steve Hogler has conducted musky spawning surveys in the Fox River just north of Voyageur Park and near the railroad bridge, where they are known to spawn.
When Great Lakes water quality declined in the early 1900s due to industrial, urban, and agricultural pollution, populations of native species like lake whitefish, lake trout, and lake sturgeon declined. Yellow perch populations, by contrast, exploded since they are tolerant of poorer water quality, high nutrients, and low oxygen (UW Sea Grant 2013, Wisconsin Department of Natural Resources Yellow Perch Fact Sheet). Yellow perch heavily used the Duck Creek area during the 1970s (Roznik 1979, Herdendorf et al. 1981). Despite their wide tolerance, yellow perch are sensitive to highly degraded water quality and other ecological disruptions; the large populations of the late twentieth century are no longer present today in the LGBFR AOC. Yellow perch eat zooplankton, minnows, and other small fish, while perch themselves are prey for predatory fish, such as muskellunge, northern pike, and bass (Wisconsin Department of Natural Resources Yellow Perch Fact Sheet). Yellow perch primarily spawn along shorelines in waters ranging from <1 m to >5 m. Spawning areas are characterized by aquatic vegetation, mud, sand, rocks, or woody debris (Lane et al. 1996, S. Hogler, pers. comm.). Yellow perch also occur in the pelagic (open water) zone of the lower bay, including Dead Horse Bay, Longtail Point, Point Sable, and UW-Green Bay, and along the Fox River, Duck Creek, and Dutchman Creek (Lower Green Bay and Fox River Area of Concern Biota Database, Wisconsin Department of Natural Resources Fish Mapping Application 2018). As a part of his UW-Green Bay Cofrin Student Research Grant, student David Lawrence discovered that Wequiock Creek, which enters the bay at Point au Sable, provides important nursery habitat for yellow perch. Areas like Wequiock Creek are especially important for yellow perch, because their most critical life stage is when they are juveniles, a life history stage where they need protected streams and open water habitat (Qualls et al. 2013, S. Hogler, pers. comm.).
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Fish species in this category include those that utilize small tributaries or streams (up to the 1 km LGBFR AOC boundary) for residency, reproduction, or for nursery habitat, including but not limited to: suckers (Catostomidae), minnows (Cyprinidae), northern pike (Esox lucius), yellow perch (Perca flavescens), etc.
Top carnivores and insectivores provide evidence of a healthy food web, while lithophilous (“stone-loving”) breeders indicate a quality stream substrate. Intolerant or sensitive species, by definition, are absent or rare in highly polluted streams, so their presence indicates habitat suitability and at least moderate water quality. Many top carnivores like northern pike, walleye, and yellow perch are economically important in addition to their value as ecological indicators. Although adults inhabit open water and shorelines of the lower bay and Fox River, northern pike migrate up small streams, tributaries, and even roadside ditches in early spring to reach inland wetlands that have standing water for spawning. Breeding adults also spawn in Great Lakes coastal wetlands along the bay shoreline (Northern Pike Fact Sheet, Jude and Pappas 1992, Qualls et al. 2013, S. Hogler, pers. comm.). Adults are known to travel inland up to 24 km to reach spawning habitat. Pike travel upstream primarily along the west shore and smaller tributaries along the Fox River, including the East River, Dutchman Creek, and Ashwaubenon Creek (S. Hogler and C. Larscheid, pers. comm.). After hatching, only about 1% of total fry and fingerling pike survive to adulthood, though the WDNR stocks millions of pike fry and fingerlings across the state (Northern Pike Fact Sheet). Unlike other fish species, northern pike can tolerate low oxygen levels in waterways making them less vulnerable to fish kills. The biggest threat to pike is the destruction of spawning habitat, though the WDNR and others have been actively restoring and improving wetlands and migratory corridors (including removing fish passage barriers) along the west shore of the bay (Qualls et al. 2013).
As adults, white and longnose suckers use rivers, shoreline areas, and open water and can grow to 50-63 cm (Michigan Department of Natural Resources 2018a, S. Hogler, pers. comm.). Suckers are toothless fish with downward-facing mouthparts that enable them to suck up food along the bottom of a waterbody, hence the name “sucker” (Michigan Department of Natural Resources 2018a, Michigan Sea Grant Suckers Fact Sheet). They primarily forage on aquatic plants, worms, insect larvae, and algae (Michigan Department of Natural Resources 2018a). In early spring, suckers migrate up both large and small rivers or tributaries and spawn over gravel areas and riffles, though white suckers also spawn in wetlands (S. Hogler, pers. comm., Jude and Pappas 1992). Longnose suckers have recently been reported in the pelagic zone of the lower bay, while white suckers have been reported in Duck Creek, Fox River, East River, Wequiock Creek, Ashwaubenon Creek, Dutchman Creek, and the pelagic zone of the lower bay including near Atkinson, Dead Horse Bay, Long Tail Point, Point Sable, and the UW-Green Bay campus (Lower Green Bay and Fox River Area of Concern Biota Database, Wisconsin Department of Natural Resources Fish Mapping Application 2018).
Minnows are generally small, narrow toothless fish up to 12 cm in length (University of Michigan Library Digital Collections, Page and Burr 2011), with species-specific diets consisting of algae, insects (e.g., midge larvae), zooplankton, other small invertebrates, or detritus (Etnier and Starnes 1993, Scott and Crossman 1998, Great Lakes Sea Grant Extension Office 2009b). Because minnows are small and often locally abundant, they are important prey for other fish (e.g., brook trout, Salmo trutta) and birds (e.g., kingfishers, mergansers; Great Lakes Sea Grant Extension Office 2009b). Minnows typically reproduce in small rivers and protected wetlands (S. Hogler, pers. comm.). Bluntnose minnows are capable of withstanding degraded waters (University of Michigan Library Digital Collections), while fathead minnow can survive in waters with low oxygen (Great Lakes Sea Grant Extension Office 2009b). Both bluntnose and fathead minnows have been frequently detected throughout the LGBFR AOC, including the Fox River, Wequiock Creek, Duck Creek, Dead Horse Bay, Baird Creek, Dutchman Creek, Ashwaubenon Creek, the lower bay, and other areas (Wisconsin Department of Natural Resources Fish Mapping Application 2018). Brassy minnows have been found in Wequiock Creek, southern redbelly dace has been recorded using the pelagic zone of the lower bay and Duck Creek, and redside dace use the lower bay’s pelagic zone, Duck Creek, and Baird Creek (Lower Green Bay and Fox River Area of Concern Biota Database, Wisconsin Department of Natural Resources Fish Mapping Application 2018). Other minnows on the list were collected by Koosmann (2016) in one or more tributaries of Green Bay between the mouth of the Fox River and the Menominee River and Hidden Springs Creek near Ephraim in Door County.
Tributary fish of Green Bay are important links in the bioaccumulation of environmental contaminants such as polychlorinated biphenyls (PCBs), pesticides, and mercury. Top predators such as northern pike and walleye are especially vulnerable to bioaccumulation of these toxins, which can cause reproductive issues or deformities (Qualls et al. 2013). Today, fish advisories based on PCBs are regularly posted at boat launches and parks that provide recommendations on safe fish consumption listed by species (Northern Pike Fact Sheet).
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Coastal meadows and beaches of the LGBFR AOC provide potential habitat for a wide range of terrestrial or semi-terrestrial invertebrates, some of which are rare or threatened. For example, Watson (pers. comm.) observed and photographed the state endangered hairy-necked tiger beetle (Cicindela hirticollis rhodensis) at the Cat Island Wave Barrier and the federally endangered rusty-patched bumble bee (Bombus affinis) at the UW-Green Bay campus during 2016-2017, both within the 1 km coastal zone of the LGBFR AOC. Populations of other uncommon species, including beach specialists like the seaside grasshopper (Trimerotropis maritima) and the state endangered Lake Huron locust (Trimerotropis huroniana), could become established if appropriate habitat is restored in the LGBFR AOC coastal zone. Native pollinators, including declining bumble bees (Bombus spp.), monarch butterfly (Danaus plexippus), Baltimore checkerspot (Euphydryas phaeton), and others have been observed by us in openings or meadows along lower Green Bay or Fox River.
The species group “coastal terrestrial macroinvertebrates” includes state and federally listed invertebrates and other uncommon or ecologically sensitive species found on beaches, wet meadows, openings, and other habitats close to the LGBFR AOC shoreline. Isard et al. (2001) described how aerial-dispersed insects accumulate along shorelines of the Great Lakes, including non-native species and pests. Their findings imply that desirable species may readily recolonize coastal habitats restored with native plant species and nesting substrates. This favorable geographic position of coastal habitats may make them especially important for conservation of native pollinators and other native insects, which have experienced widespread declines during recent decades (Potts et al. 2010, Cameron et al. 2011, Colla et al. 2012, Carvalheiro et al. 2013, Lever et al. 2014, Hallmann et al. 2017).
Two habitats of the aquatic-terrestrial interface, Great Lakes beaches and southern sedge meadows, are particularly imperiled in the LGBFR AOC. Restoration planning for these and other habitats should address the specific requirements of native invertebrates. Specifically, sandy substrates are used by many insects, spiders, and other arthropods for nests and burrows; native flowering plants are used by butterflies, bees, and other pollinators; and specialist insect herbivores like monarch, Baltimore checkerspot, and other butterflies require specific host plants for larval development. These habitat features should be incorporated into future habitat restoration plans.
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Invertebrate communities of Great Lakes coastal wetlands are diverse and complex, including open water zooplankton, bottom-dwelling zoobenthos, epiphytic invertebrates (attached to vegetation and other objects), and surface-dwelling neuston (Krieger 1992). Even for conspicuous macroinvertebrates, large knowledge gaps exist, and an in-depth assessment of species assemblages would be prohibitively expensive and beyond the capacity of available expertise. Assessment and monitoring of wetland macroinvertebrates is further complicated by the fact that most species undergo developmental metamorphosis, where the ecology of juveniles and subadults is very different from that of adults.
Despite these challenges, standardized sampling protocols have been developed that can differentiate degraded vs. relatively pristine macroinvertebrate communities in Great Lakes coastal wetlands (Burton et al. 1999, Kashian and Burton 2000, Uzarski et al. 2017). Burton et al. (1999) recognized that, regardless of environmental stress, macroinvertebrates vary significantly among different wetland vegetation zones, including outer and inner zones dominated by rushes (Scirpus/Schoenoplectus spp.), emergent marsh dominated by Typha spp., and wet meadow dominated by Carex spp. and Calamagrostis spp. (southern sedge meadow). Their research team developed different index of biotic integrity (IBI) metrics for each zone, recommending an average among zones for an overall wetland indicator. Uzarski et al. (2004) and Uzarski et al. (2017) further improved these IBI metrics. The field sampling methods recommended by Burton, Uzarski, and colleagues consist of dip net collections followed by systematic identification of a fixed number of individuals.
The IBI metrics of Burton et al. (1999) and others employ community variables like overall taxonomic richness or counts of individuals within broad groups such as Crustacea + Mollusca, Odonata, and Isopoda. In many cases, these variables showed different responses to disturbances in different vegetative zones, and subsequent studies (e.g., Great Lakes Environmental Indicator Project; Ciborowski et al. 2015) have shown that species within the groups often exhibit different responses to environmental stress. Nevertheless, several taxonomic groups, notably genera or families of Odonata (dragonflies and damselflies), mayflies (Ephemeroptera), and Sphaeridae (fingernail clams), show consistent sensitivity to environmental stress. Burton et al. (1999) also found that total taxonomic richness was consistently associated negatively with environmental stress in the Typha and inner Scirpus/Schoenoplectus zones of Great Lakes wetlands, a result that is consistent with the Great Lakes Environmental Indicator results (R. Howe, pers. comm.) that many taxa (e.g., Notonecta [backswimmers], Planorbella [a snail]) decrease or disappear at heavily stressed sites.
Our definition of “coastal wetland aquatic macroinvertebrates” excludes species assemblages of the outer Scirpus/Schoenoplectus (bulrush) zone, which is absent from the edge of many wetlands in the LGBFR AOC. Wet meadows also are rare or highly degraded in the LGBFR AOC, so we excluded this zone, at least for this report. Hence, our analysis of coastal wetland aquatic macroinvertebrates refers to macroinvertebrates of the inner Scirpus/Schoenoplectus and Typha zones, where relatively tall emergent wetland plants are dominant.
From May through October 2016, UW-Green Bay graduate student Willson Gaul conducted surveys of Odonata at seven sites within the LGBFR AOC and one (Sensiba State Wildlife Area) site just north of Long Tail Point. During 107 hours of field sampling, he identified 38 species (Table 2). Difficult species identifications were confirmed by WDNR Odonata expert Robert DuBois. Observations for which species identification was uncertain were excluded when making this list. Sampling locations consisted of fixed length transects plus an area of approximately 1.61 km (1 mi) radius around the transect locations. Only two of the recorded species (green-striped darner, Aeshna verticalis and russet-tipped clubtail, Stylurus plagiatus) are listed as vulnerable (state rank = S3 and S3S4, respectively) in Wisconsin. Highest species richness (18 species) was recorded at the Sensiba State Wildlife Area reference site, followed closely by Point au Sable (17 species) and the Cat Island Wave Barrier (13 species).
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Several small tributaries enter lower Green Bay and the Fox River within the LGBFR AOC boundary (e.g., Wequiock Creek, Mahon Creek, Ashwaubenon Creek). Although the hydrologic discharge from these watercourses is miniscule compared with the water flowing into the bay from the Fox River and, to a lesser extent, Duck Creek, these streams provide important fish and wildlife habitat and deserve to be a part of LGBFR AOC restoration efforts. Water quality in these streams is often better than that of the highly eutrophic and sediment-laden lower bay, Fox River, and main channel of Duck Creek. Given the continuing water quality issues in this ecosystem, small tributaries may serve as refugia for ecologically sensitive invertebrates and as critical habitats for spawning or juvenile development of certain LGBFR AOC fishes. Stream invertebrates also are sensitive to the effects of climate change (Hogg et al. 1996), and trends in species composition may provide evidence of broader ecosystem changes not directly attributable to the local environment.
Stream macroinvertebrates are important because they are a food source for fishes, but they also influence other attributes of stream ecosystems including nutrient cycling, decomposition, patterns of primary productivity, and translocation of biomass (Wallace and Webster 1996). Stream macroinvertebrate communities themselves are affected by many factors, including the regional species pool, physical stream morphology, and species interactions (Heino and Peckarsky 2014). Despite the well-documented ecological significance of stream macroinvertebrate communities, we weighted stream macroinvertebrates in the lower quartile of species/species groups (Table xx), largely because of their low economic importance and the limited extent of stream habitats in the LGBFR AOC.
Numerous studies have demonstrated that certain macroinvertebrates, particularly species in the orders Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera (caddisflies), are sensitive to pollution and can be used to assess the ecological condition of stream ecosystems (Lydy et al. 2000, Herman and Nejadhashemi 2015). Development of stream macroinvertebrate indicator metrics has been pioneered in Wisconsin, so details about the environmental sensitivities of local species are fairly well documented.
Pollution abatement upstream clearly is important for improving the condition of stream macroinvertebrates, but restoration of in-stream habitat also is needed for many if not all small tributaries in the LGBFR AOC. Published studies provide a wealth of general guidance for ecological restoration of impaired streams (e.g., Roni et al. 2002, Bernhardt and Palmer 2007). Effective management actions include 1) improving stream connectivity by removing dams and other barriers (Jansson et al. 2007), 2) restoring substrate features like gravel/sand riffles or woody debris (Larson et al. 2001, Schwartz and Herricks 2007), 3) restoring natural stream hydrology by reconstructing meanders, pools, backwaters, and other features lost through channelization (Rinaldi and Johnson 1997, Kondolf 2006), and 4) rehabilitating streambank and riparian features by re-vegetation or bank stabilization (Sudduth and Meyer 2006). Kitto et al. (2015), Swan and Brown (2017), and others have noted that physical changes in habitat do not always improve stream biodiversity because many native species are dispersal-limited, unable to rapidly recolonize stream segments where they have been locally extirpated. By the same token, quality upstream habitats might function as biological refugia, harboring native invertebrates that might recolonize restored sites downstream or even in the bay or Fox River.
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Muskrats (Ondatra zibethicus) are relatively common and are often considered pests because of their damage to shoreline or riparian structures. However, muskrats are a key element of emergent wetland ecosystems in North America and several researchers describe them as important “ecological engineers.” Clark and Kroeker (1993) and Davis and van der Valk (1978) noted that muskrats are the most significant vertebrate consumer of vegetation in many North American wetlands, where their activities influence vegetation decomposition (Connors et al. 2000), the proportion of open water within the wetland (Weller 1981), and availability of nest sites for birds and other animals (e.g., Hickey and Malecki 1997). Construction of muskrat houses and runways also provide important microhabitats for invertebrates (Nelson and Kadlec 1984) and colonization habitat for wetland plants (Weller and Spatcher 1965), thus increasing wetland plant species richness.
Recent surveys (Roberts and Crimmins 2010, Ahlers and Heske 2017) have shown that muskrat populations are declining across the U.S., especially in the south. Possible causes include overall wetland loss and isolation, degradation of remaining wetland habitats, changes in hydrodynamics due to climate change or water level controls, or species interactions such as disease or competition from invasive species. Benoit and Askins (1999) found that muskrats declined in wetlands dominated by Phragmites australis, so muskrat numbers on a landscape scale might be an indicator of the impacts of Phragmites on natural wetland dynamics.
Because of their potentially critical ecological role in wetland dynamics, we treated muskrats as a single-species category in our list of important population groups. The earlier RAP delisting targets (Wisconsin Department of Natural Resources 2016) also identified a target of “healthy, self-sustaining, naturally reproducing populations” of muskrats and other native furbearers.
Muskrat numbers in the LGBFR AOC can be expected to fluctuate naturally (perhaps dramatically) due to demographic factors (e.g., Errington 1951, Haydon et al. 2001) and variations in water levels in the Green Bay coastal zone. During recent relatively high water-years (2016-2017), muskrat populations appear to be thriving in Green Bay wetlands. Wolf (pers. comm.), for example, used June 2017 aerial imagery to estimate densities of muskrat structures of 0.5/ha at Peter’s Marsh, 2.0/ha at the Duck Creek Estuary and Dead Horse Bay, 2.85/ha at Duck Creek west, and 4/ha in the lagoon at Point au Sable. These numbers are high compared with similar studies elsewhere (Proulx and Gilbert 1984, Toner et al. 2010), although Bellrose and Brown (1941) reported a remarkable density of 8.65/ha (3.5/acre) in emergent vegetation zones of lakes with stable water levels.
We have no information on the long-term sustainability of muskrat numbers in the LGBFR AOC. During 2017, at least 6 local centers of abundance (separated by at least 1 km) appear to be present. While more local centers of abundance may be present in the lower bay and Fox River, especially with continued control of Phragmites, we have no evidence to suggest that a higher number is an ideal future condition. Instead, we emphasize the critical importance of sustainable local muskrat centers of abundance (separated by at least 1 km), which help insure persistence through both high and low water cycles. The standardized muskrat visual index (MVI) of Engeman and Whisson (2003) can be used to document muskrat numbers in parallel with muskrat structure surveys from air photos. On-the-ground surveys (using the MVI) will be especially important during low water years when muskrat structures are less apparent from air photos.
Other studies (e.g., Cotner and Schooley 2011) have shown that muskrats are tolerant of urbanization and some degree of invasive vegetation, so factors like wetland habitat loss, reduced wetland connectivity, and disruption of natural water-level fluctuations (Greenhorn et al. 2017) are most likely to threaten viability of muskrat populations (Ahlers and Heske 2017). Biotic factors like predation or disease also might be important, but these effects occur in natural populations and are most likely to be episodic even in undisturbed conditions. The most important management action to protect muskrats in the LGBFR AOC simply might be to protect large, contiguous areas of emergent wetland vegetation, coupled with ongoing control of invasive wetland plant species like Phragmites.
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North America supports the most diverse freshwater mussel fauna on Earth. The Mississippi River basin, in particular, contains more than three times the number of native mussel species as in the Amazon-Orinoco Basin in South America, more than three times the number of species in the entire Palearctic region (Europe and northern Asia), and more species than in any of the world’s drainage basins except the Gulf Coast region of the U.S. (Haag 2012). Freshwater mussels of the Laurentian Great Lakes are derived mainly from post-glacial colonization of species from the Mississippi drainage. Lake Michigan mussels (31 species, all in the family Unionidae) are believed to have originated from range expansions through a former connection to the Wisconsin River, which drains directly into the Mississippi River in southwestern Wisconsin (van der Schale 1963).
Unfortunately, over 70% of the word’s freshwater mussel species are either extinct or imperiled (Strayer 1983, Ricciardi and Rasmussen 1999, Watters and Flaute 2010). Not only are these filter-feeders sensitive to sediment pollution, but individuals are long-lived (i.e., populations are slow to recover from disturbances) and have complex life cycles with a larval host, usually a fish (Table xx) or aquatic amphibian like the common mudpuppy (Necturus maculosus).
The LGBFR AOC appears to have lost most, if not all, of its native mussel fauna. Dead shells are easily found along the Green Bay shoreline today, bearing testimony to a recent unionid community that has given way to invasive dreissenid mussels (Dreissena polymorpha and D. bugensis) in this highly modified, hypereutrophic aquatic ecosystem.
Unionid mussels are not mentioned in the original RAP targets for the degradation of fish and wildlife BUI (Wisconsin Department of Natural Resources 2016a), but native mussels are increasingly recognized as an important, though underappreciated and critically imperiled element of freshwater ecosystems in the Great Lakes (Metcalfe-Smith et al. 1998, Schloesser et al. 2006, Weinzinger 2017, Weinzinger et al. in prep., and others).
Weinzinger (2017) found no live mussels at a site in Duck Creek, approximately 5 km inland from the Green Bay shore. Farther upstream, however, his sampling team found more than 500 individuals of 12 species (Actinonaias ligamentina, Alasmidonta viridis, Amblema plicata, Anodontoides ferussacianus, Eliptio dilatata, Fusconaia flava, Lampsilis siliquoidea, Lasmigona compressa, Lasmigona complanata, Pyganodon grandis, Quadrula quadrula, and Strophitus undulatus). Weinzinger (2017) also found seven species (including Leptodea fragilis, not found in Duck Creek) in the Suamico River, which empties into Green Bay just north of the AOC boundary at Long Tail Point. Some of these species are restricted to streams and rivers, but others may occur along lakeshores or coastal wetlands. Nearby populations in Duck Creek and other tributaries are important because they may provide a source of individuals for re-introduction or re-colonization into the Green Bay ecosystem. Weinzinger found recent dead shells of L. fragilis (fragile papershell), A. plicata (threeridge), L. siliquoidea (fatmucket), and F. flava (wabash pigtoe) along the Point au Sable shoreline, suggesting that suitable habitat exists or at least existed recently for several species.
North American river otter (Lutra canadensis) and American mink (Neovison vison) are semi-aquatic carnivores in the family Mustelidae. Otters eat fish, crayfish, frogs, muskrats, and other animals of nearshore environments, while mink, the smaller member of this pair, consume fish, muskrats, reptiles, anurans, bird eggs, and small mammals. Healthy populations of these coastal mustelids reflect a productive ecosystem where bioaccumulation of toxins is at least tolerable. Although secretive, both North American river otter and American mink are excellent indicators of AOC condition and are valuable as harvested furbearers and “watchable wildlife.”
North American river otters are a flagship species of food-rich coastal areas and lower portions of rivers and estuaries, although they are scarce in polluted waters of heavily settled areas (Feldhamer et al. 2003). According to WDNR otter harvest records (Dhuey et al. 2016, Dhuey and Rossler 2017), eight otters were harvested in Brown County during 2015-2016, and nine were harvested in 2016-2017. Published densities of North American or European otters range from 0.7 to 5/km2 or about one otter per 2-3 km of lakeshore (Erlinge 1968). More than 12 km of shoreline (excluding the Cat Island Wave Barrier) exists along the west shore of Green Bay; along the east shore, Point au Sable has about 2.5 km of shoreline (excluding the coastal lagoon and Wequiock Creek) and the UW-Green Bay Bay Shore Woods and Beach plus Joliet Park add another 1.5 km. Although mostly privately owned, the bay shore from Mahon Creek to the South Bay Marina is more than 4.5 km. The Fox River includes more than 5 km of developed but potentially habitable shoreline. Given suitable den sites and an uncontaminated prey base, a sustainable population of 2-3 family groups (adult female and young) certainly seem possible. We observed otters at the Bay Beach Wildlife Sanctuary and at Sensiba State Wildlife Area (just north of the LGBFR AOC on the west shore) during this study period.
American mink, like North American river otter, are harvested by licensed trappers during a limited, regulated season, although unlike otters a special permit is not needed. Geographic information about mink harvest numbers are not available. However, LGBFR AOC field workers observed mink incidentally at UW-Green Bay (multiple times), Point Sable, and the Cat Island Wave Barrier, suggesting that mink populations are well-established in the AOC.
The number of coastal wetland mustelids likely can be increased most effectively by improving the availability of shelters and denning sites along the shoreline of Green Bay and contributing tributaries. Hollow trunks and logs, crevices in loose rocks, log jams, and even abandoned human structures are used by otters (Feldhamer et al. 2003). Mink numbers are strongly correlated with the amount of wetland habitat (Feldhamer at al. 2003), although availability of appropriate den sites is also important. Schladweiler and Storm (1969) reported that a single mink family in Minnesota used 20 different den sites in a 31-ha area. Bank burrows of muskrats, muskrat houses, and tree roots (especially) or hollow logs along shorelines and tributaries are commonly used by mink for shelter or maternal care (Garcia et al. 2010).
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The original BUI removal targets for the LGBFR AOC (Wisconsin Department of Natural Resources 2016a) proposed that reptiles (including snapping and painted turtles) should be sustained in “abundances sufficient to provide ecological function.” Assuming that turtles have been an integral part of the historically recent (~500 yr ago to present) Green Bay ecosystem, maintenance of viable turtle populations in the LGBFR AOC implies that their ecological function is at least partially fulfilled. Presence of viable populations themselves, unfortunately, are not clearly established today. We observed few turtles of any kind during our field surveys, although of course the methods were not targeted toward this group. Nevertheless, this is a group that we suggest deserves increased attention.
Two widespread species, eastern snapping turtle (Chelydra serpentina) and painted turtle (Chrysemys picta), are by far the most common turtles in the LGBFR AOC. Additionally, Blanding’s turtle (Emydoidea blandingii), recently delisted as a Wisconsin threatened species, has been reported in Brown County (Wisconsin Herp Atlas Project 2007). Suitable habitat (Ross and Anderson 1990) occurs in coastal landscapes such as Point Sable, Bay Beach Wildlife Sanctuary, Duck Creek Delta, Barkhausen Waterfowl Preserve, and the Malchow/Olson Tract, where mosaics of ponds, forested swamps, and wet meadows are located near the Green Bay shoreline (Joyal et al. 2001). Spiny softshell turtle (Apalone spinifera) has been verified in Brown County (Wisconsin Herp Atlas Project 2007), including in the lower Fox River in the 1980s (G. Casper, pers. comm.), and was found in the bay south of Point Sable in 2015 (S. Beilke, pers. comm.). Wood turtle (Glyptemys insculpta), officially listed as threatened in Wisconsin, favors forested streams with nearby wet meadows (Compton et al. 2002). This species may not be present in the coastal zone of Green Bay but has been found in Duck Creek and Pensaukee (G. Casper, pers. comm.) and could potentially occur at other sites along the East River or Baird Creek.
Wieten et al. (2012) demonstrated that submersed/submerged aquatic vegetation (SAV), water-lilies, cattails, and hydrologic features of drowned river mouths were associated with abundance of turtles at 56 coastal wetlands in Lakes Huron, Michigan, and Superior. Conservation of areas with extensive SAV and water-lilies (e.g., Duck Creek and Dead Horse Bay) will be important for improving the condition of turtles in the AOC. Threats from highway mortality and nest predation also need to be addressed. Surveys for locating nesting habitat may be combined with caging or fencing egg burial sites during the turtle incubation period.
Basking sites such as shoreline deadwood, sandbars, or vegetation islands have been shown to be critical for thermoregulation in turtles (Boyer 1965). These habitats are generally missing from developed shorelines in the LGBFR AOC and should be an important element of proposed beach and shoreline restoration projects.
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